(Semi) Blind Channel Estimation & Data Recovery in OFDM

Presented by: Ahmed Abdul QuadeerElectrical Engineering Department

2nd Graduates Seminar Day

Outline

Wireless Communication System

Transmitter Channel Receiver

OFDM

Problem

Transmitter Channel Receiver

X H Y = H ʘ X

X = Y ./ H

Channel Estimation Techniques

= HELLO

Training Based Technique

Transmitter Channel Receiver

HELLO ЧҒҐЮҨ

X H Y = H ʘ XY and X known

H = Y ./ X Wireless channel is time variant.

Necessary to train periodically Low Bandwidth Efficiency.

HELLO = HELLOℏℱℰℳℭ

Blind Technique

Transmitter Channel Receiver

No training used. Utilize structure of the communication system:

Finite Alphabet Set

Time Correlation

Coding

Data Transmitted = {A, B, C, D}

A 000 and B 111

t

Semi-Blind Technique

Transmitter Channel Receiver

Hybrid of Training and Blind techniques.

Training signal as well as other constraints of communication system are utilized.

Data Aided Technique

Use the refined channel estimate to detect data again. Joint Channel Estimation and Data Detection.

Use detected data to improve the channel estimate .X H

Conclusion

LOW HIGH

Trade off between Computational Complexity and Bandwidth Efficiency

Complexity

Bandwidth Efficiency

Explanation